add constant buffer for rotation

PracticeDx/PracticeDx.vcxproj

@@ -127,6 +127,7 @@
     </Link>
   </ItemDefinitionGroup>
   <ItemGroup>
+    <ClCompile Include="Timer.cpp" />
     <ClCompile Include="WinMain.cpp" />
   </ItemGroup>
   <ItemGroup>
@@ -147,6 +148,9 @@
       <ObjectFileOutput Condition="'$(Configuration)|$(Platform)'=='Release|x64'">$(ProjectDir)%(Filename).cso</ObjectFileOutput>
     </FxCompile>
   </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="Timer.h" />
+  </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>

PracticeDx/PracticeDx.vcxproj.filters

@@ -21,6 +21,9 @@
     <ClCompile Include="WinMain.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="Timer.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <FxCompile Include="PixelShader.hlsl">
@@ -30,4 +33,9 @@
       <Filter>Shaders</Filter>
     </FxCompile>
   </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="Timer.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+  </ItemGroup>
 </Project>
\ No newline at end of file

PracticeDx/Timer.cpp

+#include "Timer.h"
+
+using namespace std::chrono;
+
+Timer::Timer() noexcept
+{
+	last = steady_clock::now();
+}
+
+float Timer::Mark() noexcept
+{
+	const auto old = last;
+	last = steady_clock::now();
+	const duration<float> frameTime = last - old;
+	return frameTime.count();
+}
+
+float Timer::Peek() const noexcept
+{
+	return duration<float>(steady_clock::now() - last).count();
+}

PracticeDx/Timer.h

+#pragma once
+#include <chrono>
+
+class Timer
+{
+public:
+	Timer() noexcept;
+	float Mark() noexcept;
+	float Peek() const noexcept;
+private:
+	std::chrono::steady_clock::time_point last;
+};
\ No newline at end of file

PracticeDx/VertexShader.hlsl

@@ -4,10 +4,15 @@ struct VSOut
 	float4 pos : SV_Position;
 };
 
+cbuffer CBuf
+{
+	row_major matrix transform;
+};
+
 VSOut main(float2 pos : Position, float3 color : Color)
 {
 	VSOut vso;
-	vso.pos = float4(pos.x, pos.y, 0.0f, 1.0f);
+	vso.pos = mul(float4(pos.x, pos.y, 0.0f, 1.0f), transform);
 	vso.color = color;
 
 	return vso;

PracticeDx/WinMain.cpp

@@ -11,6 +11,9 @@
 #include <wrl.h>
 
 #include <array>    // to usd std::size
+#include <cmath>    // to use std::sin and std::cos
+#include "Timer.h"  // to use timer
+Timer timer;
 
 // global declarations
 Microsoft::WRL::ComPtr<IDXGISwapChain>          swapchain;          // the pointer to the swap chain interface
@@ -64,6 +67,29 @@ const Vertex vertices[] =
 
 };
 
+// Define constant buffer
+Microsoft::WRL::ComPtr<ID3D11Buffer>            pConstantBuffer;
+// Create constant buffer struct
+struct ConstantBuffer
+{
+    struct
+    {
+        float element[4][4];
+    } transformation;
+};
+// create constant buffer
+const float heightWidthRatio = 0.3f / 0.4f;
+float angle = 0.0f;
+ConstantBuffer cb =
+{
+    {
+        heightWidthRatio * std::cos(angle),	    -std::sin(angle),	0.0f,	0.0f,
+        heightWidthRatio * std::sin(angle),	    std::cos(angle),	0.0f,	0.0f,
+        0.0f,					                0.0f,			    1.0f,	0.0f,
+        0.0f,					                0.0f,			    0.0f,	1.0f,
+    }
+};
+
 // Define input layout
 ID3D11InputLayout* pInputLayout;
 
@@ -100,6 +126,30 @@ void DefineVertexBuffer()
     dev->CreateBuffer(&bd, &sd, &pVertexBuffer);
 }
 
+void DefineConstantBuffer(float angle)
+{
+    cb.transformation.element[0][0] = heightWidthRatio * std::cos(angle);
+    cb.transformation.element[0][1] = -std::sin(angle);
+    cb.transformation.element[1][0] = heightWidthRatio * std::sin(angle);
+    cb.transformation.element[1][1] = std::cos(angle);
+
+    D3D11_BUFFER_DESC cbd = {};
+    cbd.BindFlags = D3D11_BIND_CONSTANT_BUFFER;
+    cbd.Usage = D3D11_USAGE_DYNAMIC;
+    cbd.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
+    cbd.MiscFlags = 0u;
+    cbd.ByteWidth = sizeof(cb);
+    cbd.StructureByteStride = 0u;
+    D3D11_SUBRESOURCE_DATA csd = {};
+    csd.pSysMem = &cb;
+
+    // Create constant buffer
+    dev->CreateBuffer(&cbd, &csd, &pConstantBuffer);
+
+    // Bind constant buffer to vertex buffer
+    devcon->VSSetConstantBuffers(0u, 1u, pConstantBuffer.GetAddressOf());
+}
+
 void DefineInputLayout()
 {
     // Create input elements description, choosing whatever need to send to GPU
@@ -146,6 +196,7 @@ void drawTriangle()
 {
     DefineShader();
     DefineVertexBuffer();
+    DefineConstantBuffer(timer.Peek());
     DefineInputLayout();
     DrawPrimitive();
 }